Category: Ecology

There have been several stories recently about genetically modified mosquitoes, bred for the purpose of fighting diseases like malaria and dengue fever. These are exciting, sophisticated techniques, but in a new piece for Slate, I argue that they’re being let down by the fact that we still don’t know a lot about basic mosquito biology, like thier mating behaviour. Ecology may not be as sexy as tinkering with genes, but history teaches us that it’s vital if these approaches are to work.

But all of these recent attempts to turn mosquitoes into malaria- and dengue-killing machines have something in common: The modified mosquitoes need to have lots of sex to spread their altered genes through the wild population. They must live long enough to become sexually active, and they have to compete successfully for mates with their wild peers. And that is a problem, because we still know surprisingly little about the behavior and ecology of mosquitoes, especially the males. How far do they travel? What separates the Casanovas from the sexual failures. What affects their odds of survival in the wild? How should you breed the growing mosquitoes to make them sexier? Big question marks hang over these seemingly straightforward questions.

Heather Ferguson from the University of Glasgow studies mosquito ecology. She views the knowledge gap in this field as a significant obstacle that stands in the way of the GM-mosquito initiatives. History tells us how dismally such initiatives can fare if they are not constructed on solid ecological foundations. In the 1970s and 1980s, several groups tried to control the mosquito population by releasing sterile males that would engage females in fruitless sex. The vast majority of the experiments failed.

Their poor performance is often blamed on the fact that the males were sterilized with damaging doses of radiation. But they had many other disadvantages. Lab-bred mosquitoes are frequently reared in large, dense groups, which produces smaller, less competitive individuals. The artificial lights of a lab could also entrain their body clocks to the wrong daily rhythms, driving them to search for mates at the wrong time of the day. And in several cases, the modified males ignored the wild mosquitoes and preferred to mate with their lab-reared kin instead. These problems went unnoticed in lab tests, where the modified mosquitoes were compared with unaltered ones that had been raised in the same conditions. They seemed to be perfectly competitive, but they proved to be feeble challengers to their wild peers.

It is very easy to find the world’s most extensive marketplace – just find your nearest forest, field or garden, and look underground.

The planet’s land plants are engaged in an ancient alliance with the so-called “AM fungi” that grow into their roots. One plant might be colonised by many fungi, and a single fungus could connect up to many plants. The fungi harvest nutrients like phosphorus and nitrogen from the soil and channel them to their hosts. In return, the plants provide the fungi with the sugars and carbohydrates they need to grow.

This symbiotic partnership covers the planet in green. It’s common to 80 percent of land plants, and is credited with driving the evolution of this group some 470 million years ago. Now, Toby Kiers from Vrije University in Amsterdam has found that plants and fungi have maintained their grand alliance by setting up a strong market economy.

The most important fishes on a coral reef aren’t the impressive predatory ones or the flashy colourful ones – they’re just humble cleaners.

The cleaner fish Laborides dimidiatusis cross between a janitor and a medic. It runs special “cleaning stations”, which other fish and ocean animals visit for a regular scrub. The cleaners remove parasites from their clients, even swimming into the open jaws of predators like moray eels and groupers. They’re like living toothbrushes and scrubs. And they work hard – every day, a single cleaner inspects over two thousand clients, and some clients visit the stations more than a hundred times a day.

The cleaners, and their relationships with their clients, make a classic case study for biologists studying the evolution of cooperation. The tiny fish clearly get benefits in the form of a meal, and they enjoy a sort of diplomatic immunity from otherwise hungry hunters. On the face of it, the clients also benefit by getting scrubbed of harmful parasites. Now, Peter Waldie from the University of Queenslandhas shown how important this hygiene is.

From the ground, Heron Island looks like it has materialised out of a holiday brochure. It’s home to pristine beaches and lazing tourists, all surrounded by the turquoise waters of Australia’s Great Barrier Reef. But there’s an aspect to Heron Island that doesn’t fit with this idyllic vibe. It’s what Elizabeth Madin from the University of Technology, Sydney, has dubbed a “landscape of fear”. To see it, you need to take to the air.

Satellite images of Heron Island, freely available as part of Google Earth, depict the same vibrant colours. But around some of the reefs, there are distinct halos – light blue rings that encircle patches of rock and coral. These rings are caused animals such as fish and sea urchins, which munch on the algae and seaweed that cover the reef floor. These grazers hide from predators within the rocks and dart out to eat the surrounding algae, leaving behind a barren halo among an otherwise green landscape.

Every year, in mid-September, big brown bats throughout Colorado head for their favourite roosts, where they will spent the winter in hibernation. But some of the bats won’t sleep alone – they are carrying the rabies virus, and it will also hibernate through the winter in its slumbering host.

The rabies virus is a killer. Infections are almost always fatal, and around 55,000 people around the world succumb to the virus every year. Dogs are the leading carriers, but in North America, vaccination programmes have effectively eliminated dog rabies. Bats are another story – they are far more difficult to vaccinate and they have overtaken man’s best friend as the leading cause of American rabies.

Now, Dylan B. George from Colorado State University has shown that the rabies virus, by hibernating alongside the big brown bats, gets a free pass to the next generation.

Despite its name, the Gulf of Mexico’s Dead Zone is full with life. This region stretches over 22,000 square kilometres, an area the size of Israel. Its waters are choked by a combination of fertiliser, sewage and industrial run-offs, flowing down from the businesses that line the Mississippi. These pollutants feed large blooms of algae that ultimately rob the water of oxygen, depriving it of the ability to support fish and other typical residents. Instead, the Dead Zone has become the dominion of jellyfish.

Jellyfish congregate here in their thousands. Locals like moon jellies and sea nettles are joined by foreign travellers like the Australian spotted jellyfish. These gelatinous swarms stretch for miles, covering the ocean in a web of pulsating umbrellas and stinging tentacles. At their densest, you could scoop up a hundred jellies within a single cubic metre of water. They shut down beaches, fisheries, industries and ecosystems.

The reasons for these swarms are unclear. By overfishing, we could have removed the jellies’ main competition for food. By sinking man-made debris like vehicles and rigs, we could have created habitats for their larvae. By raising the temperature of the oceans and pumping them with pollutants, we could have created warm, oxygen-poor waters that only they can thrive in.

The jellyfish blooms are a natural phenomenon but marine biologists suspect that they are becoming increasingly common. Reports are constantly flooding in of unusual thick and large swarms, not just in the Gulf of Mexico, but all over the world from the Mediterranean to the Japanese coast. The worry is that we are witnessing a transition from an ocean full of scales, shells and flippers to one that’s ruled by jelly.

The Beatrix gold mine lies a few hours outside of Johannesburg, South Africa, in one of the richest gold fields in the world. It extends more than two kilometres underground and every year, 10,000 workers extract around 11 tonnes of gold from the mine. But recently, something living came up with the gold, a creature that has been named after Mephisto, the Devil from the Faust legend.

So far, this seems like something from a stock fantasy tale, where miners dig “too greedily and too deep”, and release an ancient unspeakable evil. Fortunately, the creature that lurks in the Beatrix mine – Halicephalobus mephisto –is just a worm, barely half a millimetre long. It’s no demon of shadow and flame, but it is an incredibly surprising find. It’s an animal that lives where no other animals were thought to exist, in the rocky underworld known as the “deep subsurface”.

The deep subsurface refers to anything deeper than 8 metres, below than the reach of rabbit warrens and tree roots. It is a hot, cramped world, high in pressure and low in oxygen, a far cry from the sun-drenched, wind-swept surface. But it’s also teeming with life. There are more microbes in the subsurface (bacteria, and the extreme archaea) than there are up top, and collectively, they might even outweigh all surface life. Put every tree, elephant and human on a giant scale, and they’d be balanced by the microscopic masses that lurk underground.

On Orchid Island, off the coast of Taiwan, green turtles come ashore to lay their eggs. A single female can deposit around a hundred eggs, and the island’s beaches are littered with these clutches. These nests are such a rich source of food that they are worth defending. And that’s exactly what the Taiwanese kukrisnake does. The females treat turtle nests like their own private larder. They guard them, and aggressively ward off rivals with a false head and dagger-like teeth.

Kukrisnakes are named for a special set of teeth. These are shaped like kukris, the curved knives that are the signature weapon of the Nepalese gurkhas. The gurkhas, renowned as brave and fierce warriors, use their kukris to behead their enemies. The kukrisnakes use their weapons merely to slit eggshells, but they can also be used in combat. People who have mishandled these snakes have been left with gushing open wounds for their carelessness.

There are several different kukrisnakes and they’re just a few of the 2,700 or so serpent species alive today. But the Taiwanese kukrisnakes are the only definitively territorial ones of the lot, and even then only the ones on Orchid Island are, and only the females. Despite a few anecdotal reports, no other snake species protects a specific resource over a long period of time. Why makes this specific population of snakes different?

This monstrous fish is a tambaqui, a close relative of the piranha. Fortunately, it doesn’t share its cousin’s flesh-eating lifestyle. Instead, the 30-kilogram tambaqui (or pacu) is a vegetarian. It swims through the flooded forests of the Amazon, eating fruits that drop from the overhanging trees. In doing so, it acts as an vehicle for the Amazon’s seeds, carrying them to distant parts of the jungle within its gut.

This is a role that we normally associate with birds or monkeys, but Jill Anderson from Cornell University has found that the tambaqui is a champion seed carrier. It can spread seeds over several kilometres, further than almost any other fruit-eating animal on record.

In June 1935, the cane toad began its invasion of Australia. Sailors brought the animal over from Hawaii in an attempt to control the cane beetle that was ravaging Australia’s sugar cane crops. It was a mistake that the continent’s wildlife would pay for. The toad did nothing to stop the beetles. Instead, it launched its own invasion, spreading across the continent from its north-eastern point of entry. As it marched, it left plummeting populations of native species in its wake.

The toads are born conquerors. Females can lay 35,000 eggs many times a year, and each can develop into a new frog in less than 10 weeks. They’re unfussy eaters and they’ll munch away on bird eggs, smaller native frogs and more. And they have large glands behind their heads, which secrete a milky poison. Local predators (or domestic pets) that try to eat them tend to die.

Now, Daniel Florance from the University of Sydney has found a clever way of corralling the cane toad invasion. He realised that humans have continued to give the toad a hand, long after we first brought them to Australia. By creating dams and troughs, we provided the toad with watery staging grounds that allowed it to spread across otherwise impassably dry land.